KEVOS® MAKEOS · Power Transmission
Flange Coupling Bolt Capacity
Can the bolts of this flanged coupling carry the torque in shear?
Shear stress in the bolts of a rigid flanged shaft coupling from torque, number of bolts and bolt circle, the bolt diameter needed, and the friction torque the bolt preload can carry instead.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Torque | N·m | Peak torque including service factor. |
| Number of bolts | bolts | Number of fitted bolts. |
| Bolt circle diameter | mm | Diameter of the bolt circle. |
| Bolt shank diameter | mm | Bolt diameter in the shear plane (fitted bolts). |
| Allowable bolt shear stress | MPa | Allowable shear stress of the bolt material. |
| Preload per bolt (friction check, 0 = skip) | kN | Bolt preload, if friction is to carry the torque. |
| Friction coefficient between flange faces | Friction coefficient between flange faces. | |
| Mean friction diameter (0 = bolt circle) | mm | Mean diameter of the contact face; 0 uses the bolt circle. |
Method and formulas
- Force per bolt = 2T ÷ (n Dbc); shear stress = force ÷ (π d²/4).
- Bolt diameter needed = √(8T ÷ (π n Dbc τ)).
- Friction capacity = μ n Fi × D_f ÷ 2.
- Example: 2000 N·m on 6 × 12 mm bolts at 150 mm gives τ = 39.298 MPa.
Limitations
- Equal sharing between fitted bolts; clearance bolts carry torque only by friction.
- Flange and hub strength are checked separately.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a rigid coupling for a higher-power drive
- Size coupling bolts
- Decide whether friction or bolt shear carries the torque
Who it is for
- Design engineers
- Maintenance engineers
- Automation engineers
What you get
- Shear force and stress per bolt
- Bolt diameter needed
- Friction torque capacity
Interpreting the result
- Use either friction (preload) or fitted-bolt shear as the design basis, not both added together.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2441–2450, 302. Topic reference; no source tables or recommended settings are reproduced.
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